Safranin O is a mixture of the two compounds shown, according to Conn. Aldrich and Gurr give only the dimethyl compound.

Safranin O is commonly used for staining Gram negative bacteria red in smears to contrast with the blue Gram positive organisms. For tissue sections it is useful as a red nuclear counterstain, and was popular at one time for staining cartilage metachromatically yellow, against red nuclei on a pink background.